1. Field of the Invention
In general this invention relates to magnetic disk drive data-storage, and in particular to a Phase-Change hard disk drive data-storage apparatus that uses stationary Phase-Change Microhead Array Chips in place of conventional ‘Flying-Heads’, ‘Rotary Voice-Coil Actuators’, or other similar types of ‘Servo-Tracking’ mechanisms to simultaneously record and/or reproduce data optically to and/or from a multitude of data-track locations that are distributed concentrically across the data-surfaces of a multitude of disk-platters comprising Phase-Change data-storage medium.
2. Description of Prior Art
Prior art teaches that magnetic-media data-storage disk drives, particularly fixed magnetic-media data-storage disk drives are valued because of several factors. Including, a disk drive's overall size (i.e., or what is sometimes referred to as form factor), a disk drive's data-storage capacity, a disk drive's random access times (i.e., or what is sometimes referred to as access time or average access time), a disk drive's cost per data-byte stored, and a disk drive's “Mean Time Before Failure” (MTBF). Further, data-containing tracks are arranged as concentric-circles on the surfaces (i.e., the data-surface) of circular shaped disk-platters (the disc media), consequently, because the outermost tracks or concentric track-circles are longer they have a greater number of magnetic data-cell domains available compared to the shorter innermost data-tracks of concentric-circles also present on the same disk-platter data-surfaces. Further, the disk-platters and there associated data-surfaces are rotated at a constant angular velocity. Consequently, the head-sliders containing data transducers will fly at a faster and somewhat higher altitude above the before mentioned disk-platters outermost tracks, where relative head to disk velocity is greatest.
However, when disk-platters and there associated data-surfaces are rotated at a constant angular velocity, therefore the head-sliders containing data transducers will fly at a slower and somewhat lower altitude above the before mentioned disk-platters innermost tracks, where relative head to disk velocity is at a minimum. One known way to increase data-storage capacity of a fixed disk drive system is to divide disk-platter data-surfaces into data-zones (i.e., sometimes called data-sectors and typically comprise of data and data-areas distributed as radial sections of concentric disk-platter data-tracks), while calibrating associated transfer data-rates to the smallest disk-platter data-track diameter dimension (i.e., innermost data-track) within each particular radially distributed data-zone (i.e., this technique is sometimes called zoned data recording).
Moreover, the number of data-sectors or data-fields within each concentric track may vary from data-zone to data-zone. In order to switch from one data-zone to a different data-zone, it is necessary for a hard disk drive to adapt itself in real-time to a different number of data-sectors and a new data-rate for the switched to and different data-zone. Other known ways to increase data storage capacity include a varying of disk rotation speed as a function of the radial position of an optical data-head transducer while maintaining a substantially constant data-transfer frequency-rate, as used in optical “Compact Disk” (CD) technologies, or as an alternative method, varying a data-transfer frequency-rate with each data-track as a function of the radial position of a magnetic data-head transducer while maintaining a substantially constant disk-rotation, as used in conventional magnetic, and non-conventional optical flying-head hard drive technologies.
Furthermore, another issue confronting the designer of a hard disk drive system is data-head positioning and data-block transfer-rates. Typically, hard disk drive data-head positioning is carried out using a ‘Head Positioner’ or ‘Rotary Voice-Coil Actuator’, and normally involves track-seeking operations for moving a hard disk drive's ‘Head-Stack’ assembly from a departure data-track location to a destination data-track location. This is done simultaneously throughout the radial-extents of all installed disk-platters and their respective data-surfaces, using various data-track following operations for causing a hard disk drive's head-stack (and consequently all data-head transducers) to follow precisely only one particular data-track during a data-block read-data or a data-block write-data disk-operation. Therefore, to provide precise head-stack positioning, during a data-track seeking and following operation, some servo information is typically provided to a Rotary Voice-Coil Actuator's tracking mechanism.
Furthermore, prior-art teaches that the previously mentioned servo information may be contained on a special data-surface written exclusively with servo-information (i.e., sometimes called a dedicated servo surface), or as an alternative method, may be externally supplied by an ‘Optical Encoder’ coupled to a head-stack assembly's positioning arm, or may be supplied from servo-information interspersed and embedded among the data-fields within each circular concentric data-track. In addition, one other approach not mentioned before is provided by a technique called the ‘Open Loop Stepper-Motor’ head-stack positioning servo technique; wherein, the positional stability of a data-head at any selected data-track location is provided by the electromagnetic detents of a hard disk drive's Stepper-Motor.
Consequently, when servo-information is embedded on a data-surface formatted for Zoned-Data-Recording, several complications may arise in the reliably of providing robust servo-head positioning information. Therefore, there must be sufficient embedded information to provide stability to the ‘Servo-Loop’ and to provide positional responses during the high-speed portions of track-seeking and track-following operations, so that velocity or position profiles may be adjusted on the fly, based on present head-velocity or head-position at the time of servo-sampling. Typically, if the servo-information is recorded at the same data-rate while in positional relationship with the recorded data-blocks, as has been conventionally employed in prior art, servo-architecture is normally complex enough to switch data-rates and servo-positions. However, if regularly spaced servo-information were radially placed across data-storage disk-platter data-surfaces, while splitting some of the data-fields, located on the aforementioned data-surfaces, into segments, data-zones, when crossed-over, could cause serious complications to arise when trying to read each ‘Split Data Field’ as a single data-block.
Furthermore, the before mentioned disk-platter's rotational velocity must be constantly monitored and carefully maintained at a predetermined constant angular velocity for the aforesaid ‘Split Data Field’ scheme to function properly; therefore, adding additional complexity to the servo-tracking system. In addition, data-fields are conventionally managed by what is normally called a ‘Data Sequencer’. Further, a Disk Controller's Data Sequencer may include an ‘Encoder and Decoder’ unit, which is used to transform “Non-Return to Zero” (NRZ) data-streams, into other, more manageable, data-formats.
For example, a three-to-two 1,7 “Run Length-Limited” (RLL) code, which is used to achieve a compression of data relative to the ‘Flux-Transition Density’ on the data-surfaces of disk-platters (i.e., 1,7 RLL coding is based upon three code-bits or groups for two non-encoded data-bits, but results in a four-to-three overall data compression-rate permitting more data to be recorded on the data-surfaces of disk-platters per the number of flux-transitions that may be contained within the magnetic domains of disk-platter data-cells).
Furthermore, prior-art teaches that a Disk Controller's Data Sequencer conventionally performs the task of decoding ‘Data Sector Overhead’ information in order to locate a desired data-sector's location, and to obtain information relating to the correctness or validity of the data being read back from a particular data-sector location. A Data Sequencer is implemented as a state-machine that will conventionally monitor all incoming data-flow in order to locate a particular data-ID ‘Preamble-Field’, a particular data-ID ‘Address Mark’, a particular data-ID ‘Sector-Field’, a particular data-ID ‘Data-Field’, and a small number of ‘Error Correction Syndrome’ bytes that are appended to each data-ID ‘Data-Field’.
Moreover, prior-art teaches that the Data Sequencer will cause the appropriate action to be taken as each of the aforementioned fields are identified and located. For example, if a data-block, contained within the ‘Data-Field’ of a particular cylinder/track's data-sector location, is being sought after, the aforementioned Data Sequencer will compare incoming data-ID ‘Sector-Field’ information with the sought after data-sector information already stored in a particular register. When a positive comparison occurs the Data Sequencer causes data-blocks read from data-ID Data-Fields, via a magnetic-transducer data-head and hard disk drive read-channel, to be sent to a Buffer Controller's ‘block buffer memory’ location, where the read data-block's ‘Error Correction Syndrome’ remainder-bytes are checked for errors, and if there are no errors detected within the read data-blocks, as determined by analyzing the “Error Correction Code” (ECC) remainder-bytes, the data-blocks are sent from the Buffer Controller's ‘block buffer memory’ location to the host-system computer, using a suitable interface such as the “Small Computer System Interface” (SCSI), or the “Integrated Drive Electronics/AT Attachment” (IDE/ATA-2) interface.
Moreover, prior-art also teaches that in conventional Magnetic or in non-conventional Phase-Change hard disk drive designs, each data-sector is individually handled in response to a specific-input from a supervisory microcontroller. For example, as a particular data-sector is read, the aforementioned supervisory microcontroller will inform a Disk Controller's Data Sequencer, whether to read, or not to read, the next contiguous data-sector into a Disk Controller's buffer cache memory. Consequently, this causes a supervisory microcontroller intervention to occur for every data-sector being processed.
Typically, this is done with a programmable ‘Sector Counter’, which is preset by a supervisory microcontroller to a desired sector count so a Data Sequencer can process data-sectors sequentially until the count in the aforementioned ‘Sector Counter’ is reached. However, some hard disk drive designs do not use, or normally include within their designs, the added complication of ‘Zoned Data-Recording’ and ‘Split Data-Fields’. For these hard disk drive designs, head-stack positioner stability is provided by an ‘Optical Encoder’ coupled between a rotary head-stack positioner and the stationary base a hard disk drive's enclosure to provide a feedback signal, which is used to appropriately position the rotary head-stack, and therefore foregoes the use of ‘Embedded Servo-Sectors’, as is conventional within some prior-art.
Furthermore, prior-art also teaches, as an alternative to the split-data recording scheme, the use of a supervisory microcontroller that has been given the responsibility of managing each ‘Split Data-Field’ layout in ‘real-time’. This leads, however, to tremendous levels of bus-traffic control between the supervisory microcontroller and a Disk Controller's Data Sequencer during read-data and/or write-data disk-operations. Precluding the supervisory microcontroller from performing other useful tasks, such as head-positioning servo-supervision, error-correction, and command-status exchanges with the host computer system, which are typically communicated over a hard disk drive's interfacing bus-structure.
Moreover, in order to function effectively the before mentioned supervisory microcontroller approach would require a separate supervisory microcontroller for data-transference, which means that at least two supervisory microprocessors would be required to implement a hard disk drive's command architecture and overall disk-operation.